题目内容：

    Both native English speakers and non-native speakers find the spelling of English is the most difficult. The English spelling system is not based on a phonetic （语音） link between sounds and letters, as is the spelling of Spanish and some other languages. Instead, English spelling is affected by the historical development of the language. Some words are pronounced in several different ways； similarly, different combinations （结合）of  letters can produce the same pronunciation.

The link between sound and spelling in English is not phonetically exact for two main reasons. First, spelling changes did not keep pace with changes in the sound system after the development of printing and of conventions （惯例）for spelling. For example, the k  in knife and the gh in right come from the Middle English period (from about 1100 to about 1500) , when they were pronounced as separate sounds. Second, there are some spelling conventions that are based on other languages. For example, during the 16th century the "b" was put into the word doubt. This reflected the Latin word, dubitare, even though the "b” was not pronounced in English.

Two further influences contributed to the illogical system of spelling. When books began to be printed in England, the newly invented spelling system was undermined （逐渐削弱）because nearly all the early London printers were foreign. They were usually paid by the line and often put additional letters into words to earn more. They regularly also added extra letters to the last word of a line to make the whole text look neater. Many of their spelling errors eventually became accepted English spellings.

There have been many attempts （试图，尝试）to reform English spelling. The author and playwright George Bernard Shaw suggested a completely new alphabet, but this had very limited success. American English has developed some of  its own spelling conventions, largely as a result of the work of spelling reformer Noah Webster. Webster attempted to get rid of some of the irregularities from the English spelling system and distance American English from British English. Nevertheless, the system as a whole remains particularly complex, and English is widely regarded as having the worst spelling of any language in the world.

1.What is the most difficult for native English speakers and non-native speakers?

2.Why isn't the link between sound and spelling in English phonetically exact?

3.Did the printers often put additional letters into words to get more money?

4.What did Noah Webster do to reform English spelling?

5.What is the passage mainly about?